1. Field of the Invention
This invention relates to ball hitch assemblies of the type commonly used on towing vehicles to be engaged by a trailer coupler and, more particularly, to a ball hitch assembly with interchangeable hitch balls and structure for preventing inadvertent disassembly of the hitch ball in use.
2. Background Art
A conventional ball hitch assembly has a hitch ball secured to a towing vehicle bumper or tow bar. Conventional trailers have a tongue with a forward coupler defining a receptacle for the hitch ball. A latching mechanism, of which there are many different types in the prior art, is engaged to maintain the hitch ball in the coupler receptacle. With the latching mechanism engaged, the hitch coupler is allowed to pivot relative to the ball hitch assembly as required when the towing vehicle is turned relative to the trailer. Typically, such ball hitch assemblies provide for relatively easy connection and disconnection of the trailer coupler relative to the hitch ball and enable pivoting of the towed trailer through a relatively wide angle about the axis of the hitch ball.
For various reasons, including strength requirements, trailer manufacturers select a particular size receptacle for the trailer coupler. The receptacle size may vary from one manufacturer to the next for the same trailer size. It is necessary to have the hitch ball sized relatively close to the size of the receptacle on the trailer hitch coupler and, therefore, it is frequently necessary to change the size of a hitch ball on a towing vehicle to accommodate different trailers.
Manufacturers offer hitch balls of different diameters. It is common to construct these hitch balls integrally with a mounting shank/center pin which is affixable to the tow bar/bumper. Commonly, the shank/center pin will have its end remote from the ball threaded to accept a locking nut. The locking nut, in conjunction with a shoulder on a midportion of the shank/center pin captures the wall of the bumper/tow bar through which the shank extends. To interchange hitch ball assemblies, the lock nut is removed from the free end of the shank which is then separable from the tow bar/bumper.
The one-piece shank/center pin and ball assemblies in the prior art have serious drawbacks. First of all, if the user intends to tow many different trailers, it may be necessary to store and have available in the towing vehicle a wide range of hitch ball assemblies. Apart from this inconvenience, it is generally relatively expensive to purchase the all-in-one ball hitch assemblies.
Another problem with the integral ball and shank/center pin construction is that it is very inconvenient to have to remove the shank/center pin from the tow bar/bumper each time a trailer requires a different size hitch ball. It is common for the threads on the shank/center pin to become damaged during use, which may make it difficult or impossible to turn the nut off of the shank/center pin end. Further, the threaded free end of the shank/center pin is exposed to the elements and commonly submerged in water so that it has a tendency to rust. This makes removal of the nut even more difficult and, in some instances, may require that the shank/center pin be cut to effect removal of the assembly.
To overcome the above difficulties, prior art ball hitch designers have devised systems employing interchangeable hitch balls. One such structure is shown in U.S. Pat. No. 4,433,854, to Smith. Smith discloses a hitch ball with an inside annular groove into which a spring biased locking pin projects to prevent separation of the hitch ball from the shank/center pin. To release the hitch ball, the user depresses the pin through an access opening in the hitch ball while drawing up on the hitch ball. The employment of moving parts, such as the slidable locking pin in Smith, makes such a structure prone to failure. If the pin jams or the spring fails, which is a likelihood after a long exposure to a wet environment, the hitch ball can separate from the shank/center pin, which then dangerously frees the trailer from the towing vehicle.
U.S. Pat. No. 4,596,406, to Van Vleet et al, shows a removable hitch ball that is held in place by a locking pin that extends entirely radially through both the hitch ball and the shank/center pin. One has the inconvenience of keeping track of separate parts, i.e. the locking pin, without which the device is inoperable. The pin, in use, is also prone to shearing, bending, or becoming locked in place, as when it rusts. The pin is also prone to working loose, falling out, and becoming lost, when the trailer coupler is not attached to the hitch ball.
U.S. Pat. No. 4,522,421, to Vance, and U.S. Pat. No. 4,201,400, to Hoogenbosch, disclose a plunger and ball structure for releasably locking a hitch ball to its mounting. These two structures have the same drawbacks as those prior art structures previously discussed, i.e. they are subject to parts breakage, loss of parts, and failure to operate properly due to exposure to weather and foreign material.
While the prior art structures have afforded the convenience of hitch ball interchangeability, they have frequently done so at the expense of safety. Because a failure of the ball hitch assembly could be dangerous not only to the passengers in the towing vehicle, but to surrounding vehicles and persons, it is of the utmost importance that safety not be compromised for the sake of convenience.